水分胁迫对大果沙枣光合特性及生物量分配的影响

选取大果沙枣1年生幼苗,盆栽于相对含水量分别为70%~75%(CK)、50%~55%(T1)、35%~40%(T2)和15%~20%(T3)的土壤中培养25 d,研究大果沙枣在水分胁迫下的光合特性变化和生物产量积累及其分配规律。结果显示:水分胁迫抑制了大果沙枣的光合作用,与对照相比,T2和T3处理导致净光合速率、叶片蒸腾速率和水分利用效率显著降低,气孔阻力、胞间二氧化碳浓度和叶绿素含量升高,而且光合午休明显,非气孔因素是干旱时大果沙枣净光合速率下降的主要原因;水分胁迫下,大果沙枣的生长受到抑制,地上部分和地下部分的干生物量积累同时降低,但地下干生物量降低的程度低于地上部分;干旱处理中,T3处理显著抑制大果沙枣的生长,但仍保持一定的生物量增加。结果表明:大果沙枣具有一定的自我调节与保护能力,在水分胁迫下大果沙枣趋于将更多的资源分配给根系,以提高根冠比而适应干旱的环境。     

紫球藻藻红蛋白的分离纯化及光谱学特性

采用4℃反复浸提、离心、硫酸铵沉淀、DEAE—Sepharose Fast Flow离子交换柱层析,从紫球藻（Porphyridium cruentum Naegeli）冻干粉中分离纯化藻红蛋白,分离纯度达到4．85,总收率51．9％;经羟基磷灰石柱层析纯化,藻红蛋白纯度达到5．10,总收率34．0％,聚丙烯酰胺凝胶电泳显示1条带。所分离纯化的藻红蛋白含有3个亚基（α、β、γ）,在可见光区545nm和560nm处有2个吸收峰,在498nm处有1个吸收肩峰。实验结果说明所分离纯化的藻红蛋白纯度符合要求。     

西南桦人工林与山地雨林的群落学特征比较

人类活动对生态系统的影响是当今生态学的研究热点之一,但对在退化生态系统上进行人工造林对地带性植被群落学特征的影响研究尚较欠缺。本文根据组成群落的植物生态学特征能对其生态环境做出准确的反应这一规则,通过样地调查法分析了林龄为12年的西南桦（Betula alnoides）人工群落的区系组成和基本的群落学特征,并与当地的地带性植被——山地雨林的区系组成和群落学特征进行了比较,从而探讨人工造林对当地天然生态系统的影响。结果发现,与天然群落相比,人类活动（人工种植西南桦林）对生态系统的植物物种的生活型谱、物种叶型谱、区系成分、物种多样性等方面的群落学特征影响不大;即使在这些方面有或多或少的差异,可能也是小环境的异质性造成的。但是人工种植西南桦林对群落的季相外貌、群落的结构、物种组成、物种丰富度以及生物量等方面有较大的影响。进行综合分析后得出结论：虽然人工造林可以缩短植被自然恢复的时间以及具有显著的经济价值,但与地带性植被相比,还是有较大的生态学差异。建议为了当地经济的发展,有必要适当发展一定面积的人工林,但规模应适度。     

野生烟草种子活力检测及物候特性观察

在烟草属（Nicotiana L．）中,野生种具有抗病、抗虫及抗逆性强等性状,是烟草抗病、抗逆育种的珍贵材料。研究野生烟草种子活力及其物候特点,对于解决烟草远缘杂交过程中的花期相遇问题以及开展抗性鉴定等工作具有重要意义,是烟草抗性育种工作的基础。     

The molecular and biochemical characteristics of proline iminopeptidase from rye seedlings (Secale cereale L.)

A proline iminopeptidase (EC. 3.4.11.5) was isolated from shoots of 3 day old seedlings. The purification procedure consisted of 5 steps: acid precipitation, gel filtration on Sephadex G-200, ion-exchange chromatography on Sepharose CL 6B, twice repeated hydrophoic chromatography on Phenyl-Sepharose HP. The enzyme was purified 404.8-fold, with the specific activity of 8.5 units mg⁻¹ of protein with recovery yield of 3%. The purified enzyme had a molecular mass of 225 kDa estimated by gel filtration and 55.4 kDa by SDS PAGE. This indicates that native enzyme is composed of four subunits. The enzyme was specific for proline β-naphtylamide among various amino acid β-naphtylamides. An optimal activity was observed at 37 °C at pH 7.75. The enzyme was thermostable up to 37 °C for 30 min. The enzyme was strongly inhibited by pHMB, E-64, heavy metal ions and partially by PMSF, DFP. The results suggest that cysteine and serine residues may participate in the enzyme activity.     

濒危药用植物八角莲生态生物学特征

通过样地调查和相关资料分析,对八角莲(Dysosma versipellis)生态生物学特征的研究表明,八角莲生境群落是以热带和温带植物为主的常绿和落叶阔叶混交疏林灌丛和竹林,上层乔灌木植物多为当地优势种。适宜生长的基质土壤为黄棕壤,pH为5.40-6.59,有机质、有效N、P、K和全N、P、K养分含量高(分别为19.36%、840 mg kg-1、46 mg kg-1、310 mg kg-1和9 970 mg kg-1、1 217 mg kg-1、2 603 mg kg-1)。繁殖障碍、遗传结构不利等自身因素和人类过度采挖、生境破坏等是导致八角莲濒危的主要原因。因此,其保育策略应以迁地保育和就地保育相结合,以迁地保育为主。     

巴尔通体分离培养特性观察

从鼠类血液中分离巴尔通体(Bartonella),观察其分离培养特性。被检鼠血为2004年收集自云南省的4个县,采用含5%去纤维兔血脑心浸液琼脂培基置于35℃含5%CO2培养箱中分离培养巴尔通体,进行观察,涂片革兰染色镜检,疑似菌落用巴尔通体属特异性引物进行聚合酶链反应(PCR)扩增特异基因片段[枸橼酸合酶基因(gltA)的379 bp片段],电泳图中出现目标带即判断为阳性菌株。从397份鼠血分离到巴尔通体47份,分离率为11.8%。阳性菌落长出时间最早为3 d,多数为1~2周,占70.2%(33/47)。阳性菌落形态随培养时间延长而改变,特点多样。PCR阳性的菌经革兰染色,镜下均可见革兰阴性小杆菌。结果可见,可先用涂片革兰染色镜检,对疑似菌落进行初筛,巴尔通体种类多、形态多样,培养时间延长,菌落形态可能发生变异,有待进一步探索。     

Root and stem partitioning of Pinus taeda

We measured root and stem mass at three sites (Piedmont (P), Coastal Plain (C), and Sandhills (S)) in the southeastern United States. Stand density, soil texture and drainage, genetic makeup and environmental conditions varied with site while differences in tree size at each site were induced with fertilizer additions. Across sites, root mass was about one half of stem mass when estimated on a per hectare basis. Stem mass per hectare explained 91% of the variation in root mass per hectare, while mean tree diameter at breast height (D), site, and site by measurement year were significant variables explaining an additional 6% of the variation in root mass per hectare. At the S site, the root:stem ratio decreased from 0.7 to 0.5 when mean tree D increased from 10 to 22 cm. At the P and C sites, where mean root:stem ratios were 0.40 and 0.47, respectively, no significant slope in the root:stem to mean tree D relationship was found over a more narrow range in mean tree D (12–15 and 12–18 cm, respectively). Roots were observed in the deepest layers measured (190, 190, and 290 cm for the P, C, and S sites, respectively); however, the asymptotically decreasing root mass per layer indicated the bulk of roots were measured. Root growth relative to stem growth would need to change with increased mean tree D to explain the results observed here. While these changes in growth rate among plant components may differ across sites, stem mass alone does a good job of estimating root mass across sites.     

The Mechanism,Thermodynamic and Kinetic Characteristics of the Microbial Reduction of Goethite Mediated by Anthraquinone-2-Sulfonate

The microbial reduction process of goethite by Shewanella decolorationis S12 was evaluated. The results showed the electron shuttle, anthraquinone-2-sulfonate (AQS), could enhance the microbial reduction. The thermodynamic and kinetic characteristics of goethite reduction by microorganisms were influenced by AQS, concentrations of iron oxide, and electron donor. Transformation between oxidized and reduced species of the electron shuttle during the microbial reduction could be newly noticed. Two interactive steps, biotic and abiotic, were involved in the microbial reduction of Fe (III) oxide mediated by electron shuttle.